3.3 Water Heater Installation Details: Garages, Pans, Supports, Attic and Under-Floor Access, & Washington's Mechanical Code Deletions

What Washington Removes from UPC Chapter 5

The 2015 UPC includes long fuel-gas appliance sections copied from NFPA 54: combustion air, vent sizing, vent connectors, and termination heights. Washington does not use them for plumbing. WAC 51-56-003 adopts the UPC except for the requirements "relating to venting and combustion air of fuel fired appliances as found in chapter 5." The Chapter 5 amendments then list the exact deletions:

UPC Chapter 12, Fuel Gas Piping, is also not adopted in Washington. Gas piping is governed by the fuel gas provisions of the mechanical code. L&I's Part 1 content list (UPC Chapters 1–10, 15, 16, and 17) does not include Chapter 12, so do not spend study time on gas pipe sizing tables for this exam.

Exam trap: A question built on "50 cubic feet per 1,000 Btu/h" or "1 square inch per 4,000 Btu/h" is combustion air math from UPC 506, which Washington does not adopt. If a Washington question asks where combustion air is regulated, the answer is the Mechanical Code.

Garages and Physical Protection (UPC 507.12–507.13)

• 507.12: Appliances may not be installed where flammable liquids are openly used, handled, or dispensed unless the design, operation, or installation reduces the chance of igniting the vapors. An installation that meets 507.13 satisfies this intent.
• 507.13 (Washington amendment): In garages, and in spaces that open to a garage and are not part of the dwelling's living space, burners, burner-ignition devices, and ignition sources must be at least 18 inches above the floor unless the appliance is listed as flammable vapor ignition resistant. Washington's wording adds "ignition sources," which reaches electric elements and controls, not only gas burners.
• 507.13.1 Physical damage: Appliances in garages, warehouses, or other areas subject to mechanical damage must be protected by barriers, elevated, or located out of the normal path of vehicles.
• 507.13.2 Outside access: An appliance in a separate enclosure within the garage that opens only from outside the garage may be installed at floor level if combustion air also comes from outside.

Support, Pans, and Ground Bases (UPC 507.3–507.5)

Remember the Washington 608.5 rule: T&P discharge may not go into the pan (Section 3.2).

Attic and Under-Floor Installations (UPC 508.4)

An attic or under-floor space containing a water heater must be accessible through an opening and passageway at least as large as the largest component of the appliance, and not less than 22 by 30 inches. Then:

1. 508.4.1 Length: Where the passageway is less than 6 feet high, the distance from the access to the appliance may not exceed 20 feet, measured along the centerline.
2. 508.4.2 Width: The passageway must be unobstructed, with solid flooring at least 24 inches wide from the entrance to the appliance.
3. 508.4.3 Work platform: A level platform at least 30 by 30 inches in front of the service side.
4. 508.4.4 Light and power: A permanent 120-volt receptacle and a light fixture near the appliance, with the light switch at the passageway entrance.

Section 507.26 adds that appliances must be located to permit service access. In attics, the passageway and service area next to the appliance must be floored.

Rooftop Appliances (UPC 508.1–508.3)

• Enclosures leave at least 30 inches between the service panels and the enclosure wall (508.1).
• Keep appliances at least 6 feet from a roof edge, or provide a guard at least 42 inches high (508.2.1).
• Buildings more than 15 feet high need inside access to the roof unless the AHJ accepts another means. Scuttles are at least 22 × 24 inches, and the access needs permanent lighting (508.3).

Putting It Together: A Garage Installation Checklist

1. Permit pulled (502.1) and FHR meets Washington Table 501.1.
2. Burners and ignition sources 18 inches up, or an FVIR-listed heater (WA 507.13).
3. Bollard, barrier, or location out of the vehicle path (507.13.1).
4. Seismic straps in the upper and lower thirds, with at least 4 inches between the controls and the lower strap (WA 507.2; Section 3.4).
5. T&P discharge full size, unthreaded, ending 6 to 24 inches above the floor or outdoors (WA 608.5).
6. Expansion tank if the system is closed (WA 608.3; Section 3.4).
7. Combustion air and venting per the Mechanical Code.